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Proceedings Paper

The optical fiber monitoring system of environmental parameters using multiwavelength and differential absorption technology
Author(s): Kaihua Wu; Kuang Yan; Zuohua Huang; Ruirong Wang
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Paper Abstract

Air pollution monitoring is an important aspect of environmental protection. The pollutants to be detected are usually more than one in air or smoke monitoring. Researching new techniques that can meet the demand of detecting the pollutants at the same time is important and necessary. The paper researched the method of detecting multi-parameters in one optical fiber gas sensing system. The system used multi-wavelength and time division multiplex technique to detect the concentration of SO2 and NO2 simultaneously based on gas' spectra absorption principle. The light differential absorption formula was deduced. The two strong and weak absorbing wavelengths were chosen as signal and reference relatively. To every gas, optical coupler and narrow-band optical filters were used to generate signal and reference light from a high brightness LED. The central wavelength of filters is identical to the strong or weak absorption wavelength respectively. The multi-channel signals were switched to one light beam using a 4x1 optical switch controlled by computer in designed time sequence. The output light after absorbing by gas was coupled on a high sensitivity PIN detector. To achieve high detecting sensitivity, the light source was modulated by a pulse signal. The power and temperature control circuits were also used to stabilize the output power and wavelength of light source. After differential absorption process, the concentration of different gas can be deduced in one set of common optical and electrical sensing system.

Paper Details

Date Published: 14 February 2005
PDF: 5 pages
Proc. SPIE 5634, Advanced Sensor Systems and Applications II, (14 February 2005); doi: 10.1117/12.573836
Show Author Affiliations
Kaihua Wu, Hangzhou Dianzi Univ. (China)
Kuang Yan, Hangzhou Dianzi Univ. (China)
Zuohua Huang, South China Normal Univ. (China)
Ruirong Wang, Hangzhou Dianzi Univ. (China)

Published in SPIE Proceedings Vol. 5634:
Advanced Sensor Systems and Applications II
Yun-Jiang Rao; Osuk Y. Kwon; Gang-Ding Peng, Editor(s)

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